Recently, organic EL devices are attracting attention and EL lighting devices are replacing incandescent lighting and fluorescent lighting. Further, organic EL systems are gathering attention as an alternative to a liquid crystal system or a plasma system in display components such as televisions.
An organic EL device is formed by laminating organic EL elements on a substrate such as a glass substrate or a transparent resin film. An organic EL element includes two opposed electrodes, at least one of which is translucent, and an emitting layer consisting of organic compounds laminated between the electrodes. The organic EL device emits light by an energy arising from recombination of electrically excited electrons and holes. The organic EL device provides high contrast images when used as a display component because it is a self-luminous device. Further, the organic EL device can emit light of various wavelengths by appropriately selecting materials for an emitting layer. Still further, the organic EL device is substantially thinner than an incandescent light or a fluorescent light and emits light in a planar form, and so has fewer installation restrictions.
The organic EL element may have a problem of marked deterioration in luminescence properties such as light-emitting brightness, luminescence efficiency, and light-emitting uniformity, as compared to an initial state after operation for a certain period of time. Such deterioration in luminescence properties results from electrode oxidation by oxygen that invades into the organic EL element, an oxidative decomposition of organic materials by heat that is generated when the device is operated, an electrode oxidation by moisture in the air that invades into the organic EL element, degeneration of organic compounds, and the like. The deterioration of luminescence properties also results from mechanical deterioration of an interface structure such as debonding caused by oxygen or moisture or by stress generated at the structural interface by different coefficients of thermal expansion in the composite elements, which is triggered by heat generation or high-temperatures during device operation.
In order to prevent the deterioration of the organic EL device, it is necessary to prevent liquid such as moisture or gas such as oxygen from invading into the organic EL element.
A technique to protect the organic EL element from contact with moisture and/or oxygen by sealing the element using a resin adhesive has been proposed so as to prevent such the above-mentioned problem.
The technique to prevent deterioration by moisture and oxygen, for example, includes measures such as covering with a sealing member over an emitting layer formed on a substrate of an organic EL element, sealing it with an adhesive, and filling a hygroscopic adsorbent into the sealed space. (Patent Document 1)